Perhaps this is the wrong forum for this, but it's to do with sleep I guess.

3 or 4 times in the last while I've woken up, having slept the whole night lying on my arm, and it's completely numb. No feeling whatsoever in it. I can still move it, but not as well as usual.

Now, once I stop lying on it the sensation starts to come back and it's back to normal within 30 seconds or so, but still, those few moments when I wake up and can't feel my arm are really scary, and also I'm worried that if I slept on a bit longer I might do permanent damage or something.

Since it's only happened in the last while, I've started to try and make sure that I sleep in a position where my arm can't get trapped.

Has it ever happened to anyone else? And am at risk from permanent damage if it happens too often?

Whenever I sleep on my arm, I get a dull ache in it which is really annoying and lasts for hours. Happens quite infrequently, but I never wake up with it completely numb. Sounds to me like you are lying on it in such a way that stops the blood flow to the arm, thereby making it numb. When you wake up and move it the blood flow returns and you can feel it again.
It is normal that you can't feel the arm for a while, but as to whether that it is dangerous, I don't know.

i think you couldnt do permanent damage to your arm.. if your arm was in this state for a while, it would develop a pain .. so the pain would eventually cause you to wake up before any read damage was done

Hmm.. don't think that's it, Garthicus. Any time it happens, I wake up in the same position: head half resting on my arm which is stretched above my head, elevated higher than the rest of my body by my pillow. I'm pretty sure it's jsut a result of cutting off the blood flow to my arm, as SuperHans suggested.

Don't visit this thread often so I hope you don't mind me butting in. I've done this as well on a good few occassions and it is usually because i've been somehow lying on the arm. The usual symptoms: completly numb arm (very wierd sensation) but feeling returns fairly quickly.

However it is not necessarily anything to worry about: first off it is not due to the blood being pinched off to the arm but is nearly always down to a trapped nerve or pressure on a nerve spot in the arm.

If I sleep with my head resting on the inside of my elbow I normally wake up with my little finger and most of my arm completely numb. This is because I'm trapping the ulnar nerve.

If I sleep with my head resting on the outside of my elbow I normally wake up with my thumb, fore, middle and ring fingers and most of my arm completely numb. This is because I'm trapping the median nerve.